Method of producing pressure tight tube and tube-seat connections



March 10, 1942;

c. A. MAXWELL METHOD OF PRODUCING PRESSURE TIGHT TUBE AND TUBE-SEATCONNECTIONS Filed May 20, 1959 s Sheets-Sheet 1 INVENTOR. MaxwellATTORNEY;

v B O March 10, 1942. c, A, MAXWELL METHOD OF vPRODUCING PRESSURE TIGHTTUBE AND TUBE-SEAT CONNECTIONS Filed May 20, 1939 5 Sheets-Sheet 2 IAfWENTOR 6 BY Car/ XW 1 NM Wm ATTORNEY.

March 10, 1942. c. A. MAXWELL 2,275,451

METHOD OF PRODUCING PRESSURE TIGHT TUBE AND. TUBE'SEAT CONNECTIONS FiledMay 20, 1939 5 Sheets-Sheet Z5 a m mlR No ATTORNEY.

March 10, 1942. c. A. MAXWELL ,2 METHOD OF PRODUCING PRESSURE TIGHT TUBEAND TUBE-SEAT CONNECTIONS Filed May 20, 1939 5 Sheeies-Sheet 4 iiii ,INVENTO ax We]! Carl A.

ATTORNEY.

March 10, 1942. c. A. MAXWELL METHOD OF rnonucme PRESSURE TIGHT TUBE ANDTUBE-SEAT CONNECTIONS Filed May 20, 1939 5 SheetQs-Sheet s INVENTOR.

ATTORNEY.

.Jength within the tube seat.

sleeve;

Patented Mar. 10, 1942 UNITED STATES -PATENT"IOFFICE1 METHOD OFPRODUCING PRESSURE TIGHT TUBE AND TUBE-SEAT CONNECTIONS I CarlA.Maxwell, Akron, Ohio, assignor to The Babcock & Wilcox Company, Newark,N. J., a corporation of New Jersey Appllcation'May 20,1939, Serial No.274,749

6 Claims.

. connectionsd It is an obJect of the method to producepressure-tighttube seat connections without imposing undesirableresidual stresses upon the operative parts of the tubes employed. Forexample,

mg. 5 is an end' elevation of the split ball expander head at the end ofthe sleeve shown in Fig. 4;

Fig. 6 is a longitudinal section showing a m ul-Q tiple ring expanderassociated with a hydraulic operator. This figure also illustrates thefirst step in the expanding method, the expander head being insertedwithin the tube to be expanded;

Fig. 7 is a longitudinal settion of the Fig. 6 apthe method may beemployed to advantage in-lO paratus, illustrating the initial expandingof the fluid heatexchange apparatus of the convection type wherein aplurality of spaced tubes are fixed to one drum wall or tube sheet attheirjnlet ends,

and to another drum wall or tubesheet at their outlet ends. The tubesnormally conduct one heat exchange fluid through another at a differenttemperature and the operating temperatures and pressures are often ofhigh degree.

Among pther objects of i the invention is the production of apressure-tight expanded ,tube seat connection in a manner which willvnot involve the high degree of skill involved with roller expanding. Q

It is also an object 01'. theinvention to provide an expanded jointwhich can be produced with Fig. 8 is a transverse section taken on theline I 8-1! of Fig. 6, looking in the direction of the arrows;

Fig. 9. is a transverse section taken on the line 9-9 oi Fig. 7,.lookingin-the direction of the arrows;

Fig. 10 is a longitudinal section of the Fig. 6

apparatus illustrating the conditions substantially at the completion ofthe tube expanding operation; p I

Fig. 11 is a longitudinal section through the hydraulic operatorillustrating the movement of fluid to effect the reverse movement of theexreat rapidity. This contributes materially to the reduction of thecost of any installation in which the illustrative methodis employed.

With the. improved method portions of the tube wall throughout thelength of the tube seat are subjected to the same predetermined working,

and the tube stressing is confined to the tube When the invention isemployed in the manupander' head; Fig. 12 is a detail longitudinalsection of a part of thepiston. construction within the hydraulicoperator;

along the plane indicated by'the line l 3-! 3 of Fig. 12 and looking inthe direction of the arrows;

.Fig.

tub are upifgrmly secured f the t sheetsemployedtoexpandtubes within/apressure yesor drum walls in pressure-tight relationship, and ,the mainportions of the tubes are not bowed by longitudinal compressionstresses. Furthermore,

1 none. of the tubes in their unsupported length are put in compressionby the expanding operations..-

The invention will be described with reference to the accompanyingdrawings, in which: Figr-l is a view. showing the tube expander inelevation with the tube sheet and the associated tube shown in se tion;

Fig. 2 is a view similar to'Fig. 1 showing the position of the expanderwhileit is moving in the direction of the -arrow i9, and after it hasportion of expander sel with the assurance that all of the expandedconnections will be pressure-tight.

' Fig. 3 of the drawingsclearly shows the re- 40 lationship of thepartsconstituting the tube expander. It'includes the mandrel gill upon whichthe expander-sleeve I 2 is slidably mounted. The annular endof thesleeve 12 is screwthreaded into a collar II which is preferably ofgreater diameter than the tube l6 into which the sleeve and the mandrelare inserted prior to the initiation: of the expanding operation. Thiscollar may be formed in two halves so as to facilitate the replacementof the sleeve l2.

theexpanding and it is. forined at one end with a recess i8 to receivethe end of the tube I6 which may project through.the wall 26 initially,

or as the result of the expanding action.

.The"intermediate portionoi the mandrel Ill Fig. 13 is a partialtransverse section taken 14 ism diagrammatic view illustrating the"facture. of the above indicated apparatus the 35 p d s and e methodwhich may be e collar acts as a stop to determine the depth of from theposition A. Thus,

2 such as the portion AB may beof cylindrical contour and of suchdiameter that the sleeve I2 is freely slidable thereon, but the sectionAC is tapered so that it increases in diameter away after the expanderis inserted in the tube l8, asv indicated in Fig. 1 of the drawings,relative sliding motion between the mandrel III and the split ballexpander head 28 causes the segments M44, inelusive, of the expanderhead to move radially and outwardly so as to expand a portion of thetube with a metal drawing action and cause it to be fitted tightly inthe tube seat, as indicated in Fig. 2 of the drawings. surfaces of thehead segments approximate ated mechanism for exerting the required pullon the expander.

n is also to be understood that the tube sheet 28 may be illustrative ofa wall kof a drum or header used in the construction of a heat exchangerwherein two drumsare directly con- 'is particularly advantageous in theconstruction.

The external spherical surfaces so as to-facilitate such action.

When a pneumatic tool, such as that'indi-' cated at 28 in Fig. 3,'exertsa pull to the right on he coupling 88 (screw-threaded upon the rigt-hand end of the mandrel as shown) the tapered section AC of themandrel is moved through the expander head 28 to cause this expandingaction, and the degree of expanding of the tube when the extended headbears against it is determined byithe position of the adjusting nut 82upon the opposite end of the mandrel. As the mandrel is pulled to theright by the tool .28 the end surfaces-of the segments of the expanderhead. abut against the right hand end of the adjusting nut 82,"andfurther movement of the mandrel to the right draws the expander headthrough the tube and expands the tube within the tube seat formed in thetube sheet 26. The adjusting nut 82 is held in a predetermined positionupon the mandrel ill by a lock nut 38. This construction permitscompensation for slight variations in internal dimensions.

, or bore of the head 28 at its position of bearlng' on the taperedmandrel portion.

The expander sleeve is preferably formed of tool steeJ/and it ishardened and drawn" from the back for spring action. There arelongitudinal segments such as those indicated at 88 and 88 in Fig. 4extending from the screwthreaded annular portion 88 to the expander headsegments 2|28, which are hardened and nected by a plurality of tubes.The method of forming tube seat connections described herein of suchheat exchangers, inasmuch as it eliminates the undesirable effect ofworking the metal at the expanded locations so that'there is an actuallengthening of the. tubes between the drums or headers. The illustrativemethod avoids the residual stresses on the tubes and the tube seatsimposed by such lengthening of the tubes.

The illustrative method involves the limiting of the initial expandingaction to a position remote from a tube end and adjacent the outersurface of a tube sheet or drum wall, and subsequent expanding action ina direction toward the tube end. Thus, if there is any lengthening ofthe tube metal of the expanded portion, such dimension addition of thetube endstakes place away from the body of the "tube.

when expanding tubes of a heat exchanger involving fixed drums, and inattempting. to expand the tubes in a direction reverse to that involvedin the illustrative method. there may be such elongations of the tubesthat adjacent tubes and tube seats will be left in a state of highresidual stress, or the tubes themselves may be actually bowed by thecompression stresses imposed. Such effects can not take place when theillustrative method is employed.-

The above described expander is'particularly' adapted to form acomponent part of. the system indicated in Fig. 14 of the drawings andit is well adapted to be actuated by the fluid pressure operatorindicated in Figs. 8-13, inclusive. This operator isillustrated asassociated with a modifled form of the expander head but it will beappreciated from the following description that it ground to size, theformer segments being formed by splitting the sleeve among longitudinallines as indicated at 42. .At the left-hand ends ofthe spring segments88 and 88 the expander head segments 2|2l are separated by oblique slitsor cuts such as that shown at 48. Thus, the expander head segments arebiased by the spring action of the segments 88 and 88,

' etc.) inwardly to a position wherein the outside diameter of theentife expander head is less than ,the inside diameter of the tube l8.This permits the expander .to be readily inserted within the tube asindicated in Fig. 1 of the drawings. Also, the diagonal or obliquesplits between the segments 2l-28, inclusive, provides forsubstantiallyuniform expanding action throughout the entire circumference :of thetube l8.

It is -to be understood that the tool 28 for operating the expanderismerely representative and that the expander may be operated by anysuitable mechanism for exerting the required pull. The tool 28, asshown, is provided with the screw-threaded socket 58 for receiving theend of the coupling '88. This coupling is held in position withreference to the tool 28 by a nut 52 which is in turn screw-threaded toreceive the socketill. The tool 28 may be a. pneumatic air hammer or anyother suitable motor opermay be equally well applied'to the expanderwhich has been described.

The double acting cylinder 88 of the operator indicated in Figs. q, 7,l0, and 11 encloses an outer piston 82 which has a close sliding fltwith the inner wall of the cylinder. This piston is rigidly connectedwith the expander mandrel 84 upon which a sleeve 88 for an inner pistonis telescopically mounted. The innerpiston 88 has sliding movementwithin the outer piston'and the sleeve likewise may have movementrelative to the'mandrel. The sleeve may thus be said to form a bearingvfor'the mandrel and the combined sleeve and mandrel unitymay'slidewithin a stufling, box 10- and the packing "secured within one end ofthe cylinder.

pressure operator are shown in their starting po-' sitions in Fig. 6,the split expander rings 84 and 88 being disposed at the smaller end ofthe frusto-conical expander portion 88 of theman drel. In thisarrangement of the elements the expander head including the mandrel andthey expander rings may be freely inserted within the tube to beexpanded with the end of the tube abutting against a reaction shoulder90 formed in the stufling box I at the end of the cylinder 60. v

The expander rings .84 and,86 are constructed of spring steel and theopenings between their 1 facing ends are offset as indicated in Figs. 6and 7 of the drawings. It will also be noted in connection with thisdisclosure that the expansion of the rings is indicated by the increasein the size of the openings.

To initiate the expanding of the tube the control switch 92 (see Fig.14) isoperated to start the motor 94 and the pump 96 s0 as to forcefluid through the inlet 98. at the end of the hollow piston rod 18.. Thefluid flows from this piston rodthrough radial ducts I00 and I02 andthen fluid under pressure then flows through the radial inlet I32 intothe chamber I 84 at the right of the main piston. This action forces theentire piston assembly .to the left and the flow of fluid from thechamber I22. through the longitudinal main piston ducts I and throughthe hollow piston I0 is reversed as indicated by the arrows in Fig. 11.This movement continues'tuntil the outer (left-hand) ends of the pins'0- H2 contact with the left-hand end wall of the cylinder. Then,. themovement of the inner piston to the left is stopped and continued move--ment of the main piston to the left interrupts the communicatidnbetween the ducts I20 and the chamber I08'between the two pistons so:that continued movement of the main piston 62/to the left is permittedonly when some'meansvof egress for the fluid entrappedv in the chamberI22 is provided. Such egress cantake' place through through horizontalducts I04 and I06 formed in the piston rod and communicating with achamber I08 between the right-hand head of the/main I piston and theinner piston 68. The inner piston 68 can not move to the left onaccountof the presence of the pins IIOI I2 which are secured to'the innerpiston in such a way that they extend through openings in the left-handhead II4 of the outer piston and abut against the lefthand end of thecylinden 60. Therefore, the main piston 62 moves to the right and thepart are ducts 140 formed in the left-hand head I I4 of, the mainpiston. These ducts communicate'with' an annular chamber I42 formed inthe left-hand face of the inner piston as indicated in, Figs. 11 and 12of the drawings. Fig. 12 shows one of these ducts above the innerpistonpin -I II and communicating with .a circular chamber I44 in which thereis located a valve-closing spring I46 surrounding the stem I48 of thepoppet valve I 50 and confined between the inner piston and an annularlocking member I52 on the valve stem.. Each chamber 144 in which a valvespring is located communicates with an annular chamber I54 immediatelyat the/base of the valve by meansof ducts) I66 which are parallel to thevalve stem. Thearrangement of these ducts is particularly indicated inFigs.12 and 13 of the drawings.

sion isclearly indicated in Fig. 7 of the drawings.

at I2I. V p

During this initial expanding operation the main piston 62- may be saidto slide along the pin IIO-I I2 fixedto the inner piston and this actioncontinues until the parts reach the posi- .tions indicated in Fig. 7wherein the left-hand head II4 of the outer piston contacts with theinner piston. 1 Atthistime the longitudinal ducts ,With the elementsarranged as above indi .cated, continuedmovement of the fluid againstthe main piston 62 in the direction of the arrows of Fig. 11 compressesthe fluid within the chamber I22 and causes it to flow through the ductsI40 and I66 to open the popp t valves. The fluid then flows toward thehollow piston rod 18 of the main piston and thence into the closed fluidcircuit, thismovement continuing until the mandrel is moved to theleft-hand limit of its path of no in" the outer piston 62 (see Figs. 6,'1, and a) are moved so that their inlet ends are brought intocommunication with the chamber I08 between the inner piston and theright-hand head of the outer piston. Thereupon, the fluid'flowing fromthepump-94 and throughthe hollow piston rod 18 flows into the chamberI22 which is clearouter ly indicated at the left-hand side of the pistonin Fig-7 of the drawings. s

Continued flow of the fluid through the longitudinal main piston ductsI20 into the chamber I22 causes both pistons, the mandrel, and theexpander rings, to move as a unit, the pistons moving toward theright=hand end of thecylinder and the expander rings being pulledthrough the tube I24 to the end of the tube seat. The expandingoperationis thus completed and the switch 92 controlling the inflow of fluid tothe of operations is repeated.

operation and the various parts of the expander apparatus are brought totheir starting positions which are indicated in Fig. 6 of the drawings,Thereupon,the expander head is moved to another tube to be expanded 'andthe entire cycl Fig. 14 indicates a system employing the above describedexpander apparatus, and operative to expand the tubes communicating witha pressure vessel such as a drum. The operator, within the drum, movesthe double acting cylinder so,

that'the expander head is disposed in operative position in a tube endand closes the expanding switch 92. This .action operates through asolenoid I60 to actuate-thefour-way valve I62 and start the motor 94 andpump 96 in such operation that the fluid flows'through the pressure lineI64 axially connected to the cylinder 60 and connected. to'the hollowpiston 18 The pump creates, enough pressure in this line to pull theexpander headithrough that portion of the tube hollow piston rod Ill isopened stopping "the flow" of fiuidi'n that direction. After each.expanding operation the entire cyland the other switch I30 then operatedto'allow fluid to; flow through-thecylinder and the pistons in themanner indicated in Fig..1l'. The

. inder and expander unit is moved from the tube within the tube seat inthe drumwall I66 and ,the pressure required to effect this operation maybemeasured by a pressure gage I68 in direct communication with thepiston chamber of the I expander cylinder and arranged so .that it maybe conveniently read by the operator. The pres. sures employed in thesucceeding expanding oppressure gage affords a visual jThis solenoid isalso pressures for the successive expanding operations adjusting of theexpanding conditions or any sures indicated are below said minimum, and

. of the prior art.

erations may also be measured and recorded by a recording pressure gageI which is in communication with the line I64. This recording comparisonof the pressures required to perform the successive expanding operationsand when the pressure required is a measure of the tightness of the tubeseat connections the operator may readily check the efiectiveness of hiswork as it proceeds. In the event that he finds that the pressurerequired to expand a certain tube is less than that, which is necessaryto produce a pressure-tight connection, he may repeat the expandingoperation-oi that tube after adjusting the stop "8 at the end of themandrel 64 so that the expander rings will ride further up upon thetapered part of the mandrel. 4

The closing of the switch I30 to bringthe expander head back to itsstarting position reverses the flow through the four-way switch I02 bythe energizing of an opposed solenoid I12. This solenoid has as itsarmature or core, the switch-rod I" connected by the link I16 with thestem I18; in series with a circuit which starts the operation of thepump 94 forcing the fiuidthrough thereturn line I80 to the radial inletI32 of the expander cylinder and continues such flow until the parts ofthe expander are brought to their starting positions. Thereupon, thereturn switch I30 is opened.

The motor and pump unit ispartieularly designed to meet the requirementsof hydraulic installations which-call tor a pump automatically providinghigh operating pressures as they are required in the work to be done.includes a low pressure pump and a high pressure pump directly connectedto the shaft I06 of the driving motor 94, and above the} pump there is arelief .valve I80, a check valve I90, and -a bypass valve I92 arrangedfrom left to right in-the order named. In Fig. 14 the inlet tor both thehigh pressure and low pressure pumps is at the bottom and a pressureline I94 is indicated as extending from the valve assemblydirectly tothe four-way valve I62 which controls I the movement of the fluid in thelines connected with the expander.

.The method eiiected by the described apparasively brought up to thepressure requirement for effecting separate and successive tubeexpanding seat in one drum or 1 to all oi the details thereoii Theinvention is rather to be taken as of a scope commensurate with thescope of the subjoined claims.

This application is limited to method claims, and the apparatusdisclosed herein is claimed in a co-pending divisional application,394,758, filed May 23, 1941. r

What'is claimed is:

1. A method of manufacturing fluid heat exchange apparatus involving aplurality of drums or headers connected by a multiplicity of spacedtubes adapted to be exposed to a fluid heat exchange medium, the methodcomprising the fitting of the opposite ends of the tubes into tube seatsformed in the walls of the drums or headers with each tube having oneend fitted in a tube header and its opposite end fitted within a tubeseat in the other drum or I in the same direction tus includes theemployment of a fluid' succesoperations-on tubes in the same tube sheetor drum wall, involving the determination of minimum pressure necessarytooproduce a connection which will be pressure-tight under predeterminedoperating conditions, the measuring of the fluid one of such operationsfor which the fluid presreexpanding the pertinent tube under said aditsexpanding up to said minimum.

Although the invention has been illustrated anddescribed with referenceto tubes of circular cross section, the system-and the apparatus invvolved may, by jelatively minor rations, be advantageously sed toexpandtubes which are no t circular incross section. This result cannot besecured with the rotary types of expanders Whereas, the invention hasbeen described with reference to certain particular embodimentsindicated in the accompanying drawings, .is'to header, expanding theends of the tubes fitted into one drum or header to secure those, ends,

and then expanding the opposite ends of the same tubes in the tube seatsof the other drum orheader by initiating the expanding of each tube endonly at a position adjacent the outer surface of the drum or header wallto lock the tube to its tube se t atthatposition and continuing suchexpan progressively toward the inner wall of the drum or header andtoward the adjacent tube end, said continuing of the expanding beingaccompanied by drawing of the tube metal and from the locked positiononly.

2.'The method of operating a tube expander which 0 i e1 The assembly cmprises positioning the expander r e y within an end portion oi a. tubefitted within a tube seat, initially forcing, the pressure exertin partof the expander into contact with the tube at a position spaced fromsaid end of the tube and the adjacent end or the tube seat, operatingthe ,expander to expand the tube at that position and to initially lockthe tube to the tube vseat at'safd position and then withdrawing theexpander and simultaneously and progressively expanding and drawing thetube from said position toward the adjacent end of the tube, said'withdrawing oi theexpander taking place while the expander is in itsexpanded condition so that the withdrawing of the expander produces thedrawing of the tube metal toward the adjacent end of ,the tube from thelocked position only..-

3. The method of producing expanded and drawn tube and tube sheetconnections,,the method comprising the employment of fluid pressure insuch a we. that the pressure involved in each tube expand ng and drawingoperation continuous y over the thickness of the tube seat is a measureof thetightness of the tube and tube sheet connection produced, eachsaid operation including initially the locking of a tube to its tubesheet only at a position' adjacent the tube sheet'surface 'n'iost remotefrom the nearest end of the tube,andfthe subsequent drawing of the .tubemetal only from the locked position toward the adjacent tube end,determining the minimum fluid pressure required to produce a pressuretight connection "between the tube and the. tube-sheet,

{measuring-the fluid pressure for each tube expanding and drawingoperation, adjusting conditions of the expanding and drawing operationswhich have been indicated as involving pressures below said certainminimum, and repeatingWhe below-minimum expanding and drawing operationsunder the adjusted conditions.

be appreciated that the, invention is not limited 4- A method orsecuring .tubesto tube sheets or other metallic walls of fluid heatexchange apparatus, the method comprising the employment of a fiuidsuccessively brought up to the pressure required for effecting separateand successive tube expanding and drawing operations on-the end portionsof tubes fitting within tube seats in the same wall, each of saidoperations including initially the locking of a tube to its tube sheetor wall only at a position adjacent the wall surface most remote fromthe nearest "end of the tube and the subsequent drawing of the tubemetal only from the locked position toward the adjacent tube end,determining the minimum pressure necessary to produce a connection whichremains pressure tight under predetermined operating conditions,measuring the fluid pressures for the successive expanding operations,adjusting the expanding and drawing conditions of any of said operationsfor which the fluid pressure is indicated as below said minimum, andre-expanding and re-drawing the pertinent tube under said adjustedconditions to bring the fluid-pressure for its expanding at least up tosaid minimum.

5. The method of producing a pressure tight connection between apressure chamber and a tube having an end portion fitting withinatubeseat opening formed in a Wall of the chamber, the method consistingof the simultaneous acts of expanding and drawing the tube metal withinthe tube-seat, said simultaneous actsor expanding and drawing beinginitiated in a narrow circumferential zone of the inner surface of thetube at a position spaced from the nearest end of the tube and spacedfrom the tube seat end adjacent thereto to lock the tube to the wall atthat position only, the drawing being continuous Within the tube-seatand in a direction away from the locked position only and toward theadjacent end of the tube. the initial expanding and drawing locking thetube-seat portion of the tube to said wall in order that subsequentdrawing will not set up tube stresses in the main body of the tubeexternally of the confines of said wall.

6. The method of expanding the end portion 1 of a metal tube into a tubeseat formed in a metal wall, the method comprising initially expandingand drawing the tube in a narrow zone limited to a position adjacent thewall surface at the greater distance irom the adjacent tube end to lockthe tube to the wall at that position, and then continuing the sameexpanding and drawing operation with the same degree of expansionprogressively toward the opposite surface of said wall and away fromsaid locked position toward the-adjacent end of the tube, the expandingaction and drawing action being limited to a narrow circumferential zoneof the tube at all stages of the continued expanding.

CARL A. MAXWELL.

